Electromagnetic interference (EMI) emissions from power supplies are an important problem and are often the cause of redesigns or additional costs in circuit design. EMI emissions are usually reduced by using control schemes such as zero voltage switching, valley switching, and frequency jittering.
Other methods to create frequency jitter include oscillators with capacitor switching as disclosed in U.S. Pat. No. 7,026,851 (Yang et al), dual oscillators as disclosed in U.S. Pat. No. 6,107,815 (Balakirshnan et al) and U.S. Pat. No. 6,229,366 (Balakirshnan et al), and current source modulation as disclosed in U.S. Pat. No. 6,249,876 (Balakirshnan et al).
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